Material and methods

Wood taxonomy is based on Lepekhina (1972), who revised the nomenclature and taxonomy of Paleozoic woods worldwide. The wood has been described, when possible, in accordance with the list of microscopic features for softwood identification (Richter et al ., 2004) and the Greguss' glossary of terms (Greguss, 1955). The new material consists of 5 specimens which were collected in the fossiliferous locality known as Quebrada de la Mina, located at 31°50´34´´ S and 68°37´57´´ W in the eastern margin of the Sierra Chica de Zonda (figure 1). These specimens were compared with the holotype from Las Lajas locality (see Brea and Césari, 1995). Stratigraphically, the fossiliferous bearing strata correspond to the upper part of the Jejenes Formation, which is suggested to be early late Carboniferous in age. All the specimens are silicified (chalcedony) displaying fissures filled with carbonatic material. Wood fragments were cut in thin sections in the three planes usually used to study their anatomy. Cellulose acetate peels were also made, with poor results compared to thin sections. Good results were obtained from macerations of small wood fragments. Samples were first placed in HF 75%, washed with water, and then mounted in glycerine-jelly. These preparations allowed the observation of fine details such as cross-field pits and ray cell walls thickenings (figures 2.J, 2.K, 2.L).